The invention relates to a pedal-travel sensor device.
The published, nonexamined German patent disclosure DE 34 11 455 A1 has disclosed a transducer shaft which can be rotated by the accelerator pedal of a motor vehicle counter to a restoring spring device. In order to detect the pedal position, the transducer shaft cooperates with a rotation angle sensor which supplies an electric pedal-travel signal that corresponds to the position of the accelerator pedal and therefore to the desired drive power.
In motor vehicles, in particular in motor vehicles with an automatic transmission, it is frequently necessary when there is a forceful depression of the accelerator pedal for an electrical shifting signal to be produced, particularly so that during the acceleration, the transmission is electrically downshifted by one gear. A corresponding shifting signal is required for this. When there is excessive pressure past a particular rotation angle of the pedal, this shifting signal is produced by means of an electrical switching contact. In order to prevent an undesirable shifting-back, the electrical switching point must be preceded by a mechanical resistance, i.e. a clearly perceptible increase in the reaction force on the accelerator pedal. A switching point of this kind is frequently referred to as kick-down switching. In the patent disclosure cited above, rolling bodies in a guide cage are provided for this purpose, which cooperate with a bearing surface in the housing upon which the path of the rolling bodies is determined and which has ramps disposed at a particular rotation angle. If the rolling bodies, which are prestressed against the bearing surface are moved counter to the initial stress from a first level to a second level via the ramps, then the force increase required for this produces a perceptible mechanical resistance in the pedal, which corresponds to the switching point.
The published, nonexamined German patent disclosure DE 43 31 902 A1 and the British patent GB 2 281 957 likewise have disclosed a pedal-travel sensor device with the so-called kick-down embodiment.
The published, nonexamined German patent disclosure DE 44 22 232 A1 has also disclosed a pedal-travel sensor device in which an abrupt increase in the pedal force occurs in an intermediate position and in which a shifting signal is produced by a switch at the location with the force increase.
The pedal-travel sensor devices disclosed in the above-mentioned patent disclosures have the disadvantage that the cost for producing these pedal-travel sensor devices is very high and the costs for adjusting the switching point and also for associating the switch with the actuation position having the force increase are high and in spite of this fact, are encumbered with large tolerances.
The published, nonexamined German patent disclosure DE 195 36 699 A1 has disclosed a pedal-travel sensor device with a kick-down mechanism and a switch. The kick-down mechanism and the switch are disposed in a housing which can be very easily connected to the support structure supporting the pedal. As tests of this housing containing the kick-down mechanism and the switch have shown, the association of the switch with the kick-down action point are tied to high costs and considerable switching tolerances in this embodiment as well.
Embodiments have also been proposed in which balls are provided which are loaded radially outward against an adjusting body in a housing by means of a compression spring. In addition, the adjusting body also has a bracket attached to it, which is loaded against two contact strips by means of a spring. Depending on the position of the adjusting body, the bracket comes into contact with the contact strips or the bracket is lifted up from the contact strips. However, this proposed embodiment has the disadvantage that it is quite expensive to produce because a relatively large number of expensive components is required and in particular because the bracket must be guided in a guide provided on the adjusting body. The guide of the bracket has the serious disadvantage that in order to prevent a jamming between the bracket and guide, there must always be play between the bracket and the guide. This play involves very undesirable tolerances in the adjustment of the electrical switching point and these tolerances are unacceptable to many clients.
The pedal-travel sensor device according to the invention has the advantage over the prior art that the cost of manufacturing the force alteration device, in particular the association of the switching point with the force increase in the intermediary position, is quite low and a very precise association of the electrical switching point with the force increase can be achieved. Because it is very insensitive to wear, the association is constant over a very long time. Because there is no friction between the at least one leaf spring and the mounting means or between the least one leaf spring and the actuating member, in particular no friction in a guide, there is also no frictional wear that leads to a switching imprecision. One particular advantage is that the leaf spring does not have to be moved as a whole, but rather the leaf spring can be clamped with one end stationary and as a result, the electrical switching point can be precisely determined.
If the current loop is routed via a total of two leaf springs, then the current loop can advantageously be produced in a particularly simple manner.
If the current loop is embodied so that only one of the two leaf springs lifts up from a contact surface, then this has the advantage that only this one leaf spring has to be precisely dimensioned with regard to its structural length and its adjusting location. Certain tolerances in the other leaf spring therefore have no influence on the electrical switching point.
If the end of the contact surface where the at least one leaf spring protrudes beyond an end edge of the contact surface is provided with a protrusion that projects further in the direction of the leaf spring so that the end region of the leaf spring oriented toward the end edge does not come into direct contact with the end edge of the contact surface, then this has the advantage that because the actuating member is preferably composed of a relatively soft plastic, the leaf spring is protected even in the event of a very frequent switching, which has a favorable influence on the service life of the pedal-travel sensor device as a whole.
The lifting device advantageously achieves the fact that the at least one leaf spring is lifted up from the contact surface or is placed onto the contact surface in a manner that is gentle to the materials. Another advantage is that a friction acts on the end region of the leaf spring oriented toward the contact surface only if the current loop is closed. If the current loop is open, then no friction occurs on the leaf spring, which considerably reduces the wear and tear on the leaf spring and thereby significantly increases the service life of the pedal-travel sensor device.
If the leaf springs and the respectively associated connections are manufactured out of a single piece of material, in particular a thin sheet metal strip, then this has the advantage that particularly few components are required on the whole.
Also the embodiment in which the contact surfaces are provided on the mounting means achieves the advantage that particularly few componentsxe2x80x94and nevertheless ones which are easy to producexe2x80x94are required if the electrical connection and the contact surface associated with the connection are made of one piece, in particular stamped, out of a single component, preferably a single sheet metal strip.
If the actuating member support surface is provided on the actuating member and the mounting means support surface is provided on the mounting means, then through the simple insertion of a securing element between the mounting means support surface and the actuating member support surface, the force alteration device can be very simply assembled of only a few easy-to-produce components.
If the securing element is embodied in the form of a clamp, the force alteration device can be assembled very easily and a uniform and symmetrical force distribution is obtained between the mounting means and the actuating member.
If the actuating member is provided with a lateral hole which contains an expanding spring and at least one rolling body, in particular a ball, wherein the rolling body is pressed against the securing element by the expanding spring, then this offers the advantage that the securing element can constitute a step so that during a movement of the actuating member, the rolling body is pushed over the step, thus very easily obtaining a desired, precisely determined jump in force.